Answer

The sine of an angle is equal to the cosine of its complementary angle.

Work Step by Step

1. Set up calculator in degrees
$\sin15^{\circ}\approx0.2588$
$\cos75^{\circ}\approx0.2588$
2. Pick up more examples
$\sin10^{\circ}=cos80^{\circ}\approx0.1736$
$\sin53^{\circ}=cos37^{\circ}\approx0.7986$